Specifications

DP83848Q-Q1
www.ti.com SNLS341C –MARCH 2011–REVISED MARCH 2015
The BMSR also provides status on:
• Whether or not Auto-Negotiation is complete
• Whether or not the Link Partner is advertising that a remote fault has occurred
• Whether or not valid link has been established
• Support for Management Frame Preamble suppression
The Auto-Negotiation Advertisement Register (ANAR) indicates the Auto-Negotiation abilities to be
advertised by the DP83848Q-Q1 . All available abilities are transmitted by default, but any ability can be
suppressed by writing to the ANAR. Updating the ANAR to suppress an ability is one way for a
management agent to change (restrict) the technology that is used.
The Auto-Negotiation Link Partner Ability Register (ANLPAR) at address 0x05h is used to receive the
base link code word as well as all next page code words during the negotiation. Furthermore, the ANLPAR
will be updated to either 0081h or 0021h for parallel detection to either 100 Mb/s or 10 Mb/s respectively.
The Auto-Negotiation Expansion Register (ANER) indicates additional Auto-Negotiation status. The ANER
provides status on:
• Whether or not a Parallel Detect Fault has occurred
• Whether or not the Link Partner supports the Next Page function
• Whether or not the DP83848Q-Q1 supports the Next Page function
• Whether or not the current page being exchanged by Auto-Negotiation has been received
• Whether or not the Link Partner supports Auto-Negotiation
5.3.1.3 Auto-Negotiation Parallel Detection
The DP83848Q-Q1 supports the Parallel Detection function as defined in the IEEE 802.3u specification.
Parallel Detection requires both the 10 Mb/s and 100 Mb/s receivers to monitor the receive signal and
report link status to the Auto-Negotiation function. Auto-Negotiation uses this information to configure the
correct technology in the event that the Link Partner does not support Auto-Negotiation but is transmitting
link signals that the 100BASE-TX or 10BASE-T PMAs recognize as valid link signals.
If the DP83848Q-Q1 completes Auto-Negotiation as a result of Parallel Detection, bits 5 and 7 within the
ANLPAR register will be set to reflect the mode of operation present in the Link Partner. Note that bits 4:0
of the ANLPAR will also be set to 00001 based on a successful parallel detection to indicate a valid 802.3
selector field. Software may determine that negotiation completed via Parallel Detection by reading a zero
in the Link Partner Auto-Negotiation Able bit once the Auto-Negotiation Complete bit is set. If configured
for parallel detect mode and any condition other than a single good link occurs then the parallel detect
fault bit will be set.
5.3.1.4 Auto-Negotiation Restart
Once Auto-Negotiation has completed, it may be restarted at any time by setting bit 9 (Restart Auto-
Negotiation) of the BMCR to one. If the mode configured by a successful Auto-Negotiation loses a valid
link, then the Auto-Negotiation process will resume and attempt to determine the configuration for the link.
This function ensures that a valid configuration is maintained if the cable becomes disconnected.
A renegotiation request from any entity, such as a management agent, will cause the DP83848Q-Q1 to
halt any transmit data and link pulse activity until the break_link_timer expires (~1500 ms). Consequently,
the Link Partner will go into link fail and normal Auto-Negotiation resumes. The DP83848Q-Q1 will resume
Auto-Negotiation after the break_link_timer has expired by issuing FLP (Fast Link Pulse) bursts.
5.3.1.5 Enabling Auto-Negotiation via Software
It is important to note that if the DP83848Q-Q1 has been initialized upon power-up as a non-auto-
negotiating device (forced technology), and it is then required that Auto-Negotiation or re-Auto-Negotiation
be initiated via software, bit 12 (Auto-Negotiation Enable) of the Basic Mode Control Register (BMCR)
must first be cleared and then set for any Auto-Negotiation function to take effect.
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